The medical center says the infection that killed 60-year-old molecular genetics Professor Malcolm J. Casadaban on Sept. 13 may be connected to bacteria called Yersinia pestis that he researched, and which causes the plague.

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The medical center says the bacteria he worked with was a weakened strain that isn't known to cause illness in healthy adults. The strain was approved by the Centers for Disease Control and Prevention for laboratory studies.

An autopsy found no obvious cause of death but did find the presence of the bacteria. More tests are planned. No other illnesses have been reported.

The university notified Casadaban’s family and friends about a potential danger after they identified the bacteria during an autopsy, even though the bacteria would have a limited effect on healthy individuals. As a precaution the Chicago Department of Public Health dispersed antibiotics to them.

The Chicago Department of Public Health says there's so sign of any spread after the possible plague-related death of a University of Chicago scientist.